C
C CONNECTOR
A bayonet-locking connector for coax; C is named after Carl Concelman.
C/N
Carrier-to-noise ratio.
C4
See Controlled-collapse Chip Connection.
CA
IC part number prefix indicating RCA Solid State Division
CA
Cable
CACS
Comprehensive Automobile Control System
CAD
Computer Aided Design
CALL WAITING
A feature that signals you with a tone when you have an incoming call while you are on the phone.
CALLBACK
A feature, active during LAN Distance connection establishment, in which the answering workstation re-initiates the connection by placing a call back to the dialing workstation. The original dialing workstation must be a LAN Distance Remote workstation. This feature provides a level of security and can be used to manage telephone charges by placing call control at the answering workstation. See Callback Type.
CALLBACK TYPE
The method, fixed or variable, of obtaining the Call back telephone number. It determines whether the telephone number is already configured or if it is supplied by the dialing user at connection time. See Fixed Callback and Variable Callback.
CAMP-ON
A feature (of the AT&T Merlin Legend system) that you use to hold a transferred call at a busy extention and put the call through automatically when the extension id free.
CAN
Controller Area Network
CAPACITANCE
A measure of a cable's ability to store an electrical charge and to withstand changes in voltage. The combination of the dielectric constant with the thickness of the insulation provides the capacitance rating. This rating is for a single twisted pair, but it is also influenced by the rating of adjacent twisted pairs. Each pair of wires in a twisted pair has its own capacitance. When twisted pair is used in digital communications, this effect can distort the shape of the digital signal's square wave. This distortion can cause errors and prevent digital communications. PVC-jacketed cable provides the most unacceptable levels of capacitance, while Teflon-jacketed cable has the most acceptable levels.
CARBON COPY
A remote access technology in which keyboard and screen data are routed between two workstations across a WAN connection.
CARD
1) A printed-circuit card (board). 2) A printed-circuit-card (board) assembly - in the sense that the card (printed-circuit board) is physically the main component of a printed-circuit-card assembly.
CARD INFORMATION STRUCTURE
(CIS) A data structure written on every PC Card that complies with the PCMCIA standard. CIS contains configuration information about the PC Card and communicates it to the computer.
CARD SERVICES
The software interface that coordinates traffic among the computer and the PC Cards, sockets, and system resources.
CARRIER
The base signal used to transmit data across a telephone line. The modem modulates this signal (alters its frequency or phase) to encode the data to be transmitted.
CARRIER DETECT
(DCD) An RS-232 control signal (on pin 8) which indicates that the local modemis receiving a signal fron the remote modem. Also called Received Line Signal Detector (RSLD).
CARRIER SENSE MULTIPLE ACCESS WITH COLLISION AVOIDANCE
(CSMA/CA) Very similar to CSMA/CD, in that a particular station listens for a quiet cable before sending. However, a sending station does not continue to monitor the network once a transmission has begun. The CSMA/CA scheme never has knowledge of collisions. Error recovery may be compensated for in the data link or network layer, but there is no strict requirement. The usual method of recovering from lost data, i.e., using timeouts due to collision at the application layer, is rather time-consuming and, as a result, CSMA/CA is rarely implemented.
CARRIER SENSE MULTIPLE ACCESS WITH COLLISION DETECTION
(CSMA/CD) The access protocol used in 'Ethernet' LANs. CSMA/CD is the foundation of IEEE 802.3 standards as well as Ethernet II standards developed by Digital, Intel, and Xerox. The protocol was originally developed in 1976 by Robert Metcalfe and David Boggs of the Xerox Palo Alto Research Center. Collision Detection means that each station first "listens" to the network, sending a message only if it is quiet-in other words, if no traffic is currently on the network bus. If the bus is not quiet, the station waits a random amount of time before listening again. During and after a message has been transmitted, the device listens to the line to determine whether its message packet has collided with another packet. If a collision is detected, both sending stations wait a random (but different) amount of time before resending their message packets. The random wait time used to determine when to retransmit a packet uses a rule known as the truncated binary exponential backoff. The wait time is calculated as a random integer x in the range of 0 < x < 2y where y = min(z, 10); z is the retransmission attempt sequence number (there could be several retransmissions before one is successful). Once the time is calculated, x "slot times" are waited. The slot time is defined so that it will be larger than the sum of the physical round-trip propagation time and the MAC layer jam time. The jam time is the amount of time spent broadcasting a jam signal once a collision is detected. The jam signal lets other nodes on the network know that a collision has occurred. One drawback to the exponential backoff algorithm is that it operates on a LIFO (last in, first out) basis, which means nodes with few collisions may send before a node that has been waiting longer. The transmitting node transmits data by encapsulating the data in a frame with the destination node address at the head of the frame. All nodes receive the frame, but only the node with the destination address reads the data. Only one transmitter is on the line at any one time. The Ethernet IEEE-802.3 standard uses CSMA/CD technology. See Ethernet, Access Protocol, and Carrier Sense/Multiple Access.
CARRIER SENSE MULTIPLE ACCESS WITH COLLISION ELIMINATION
(CSMA/CE) A distributed, contention-based access method that purports to guarantee no data collisions. The CSMA/CE algorithm is proprietary, invented by John McHale of Networth, Inc. Like CSMA/CD and CSMA/CA, CSMA/CE first listens for quiet on the network. Once a quiet state has been detected, an additional wait period is inserted. This additional wait is in the microsecond range. It is termed the Deference Slot Time (DST). The DST is determined by a signal-processing algorithm that is executed locally at the station's controller. The DST is key to eliminating collisions. If several stations are all waiting when the network becomes idle, the stations do not all try to send their messages at that same moment. Instead, each station waits an additional period of time (DST) before attempting transmission. A unique DST is determined for each station since it is calculated using location-specific information. If the network becomes busy while a station is counting down the DST, then that station will wait until the next idle state and start again. The DST is calculated each time a packet is transmitted, but the DST calculation is embedded in hardware and takes place in a matter of nanoseconds, which does not hamper efficient communication.
CARRIER SENSE/MULTIPLE ACCESS
(CSMA) Utilized by both the IEEE 802.3 and Ethernet standards. Ethernet is not the same as the IEEE 802.3 standard. Ethernet is based on the experimental ALOHA Network designed in the early 1970s at Xerox's Palo Alto Research Center (PARC). The CSMA mechanism has been further refined by the development of Collision Detection (CSMA/CD), Collision Avoidance (CSMA/CA), and Collision Elimination (CSMA/CE) technologies.
CARRIER-BAND LINK
1) A communication link with a single channel whose signal modulates a carrier frequency. Example: Data Highway II link. 2) Contrasted with broadband link and baseband link.
CASCADE
When the virus is memory-resident on a machine with a CGA or VGA monitor, and the system clock is set to a date in the "Fall" (September-December) of 1980 or 1988, all characters fall to the bottom of the screen.
CASCADE CONNECTION
A series connection of amplifier stages or links in which the output of one stage feeds the input of the next.
CAT
Concatenate (view) a file
CATEGORY 1 CABLE
See Level 1 Cable
CATEGORY 3 CABLE
See Level 3 Cable.
CATEGORY 5 CABLE
See Level 5 Cable
CATENET
A number of networks linked in series, through gateways, that pass information between each other by using a communication protocol. A network in which hosts are connected to networks with varying characteristics, and the networks are interconnected by gateways (routers). The Internet is an example of a catenet. See IONL.
CAU
Control Access Unit. See Star Wired Ring.
CBA
Cell-Based Aray
CBGA
Ceramic Ball Grid Array - See Ball Grid Array.
CC
C compiler
CCD
See Charge-Coupled Device.
CCI
Cybercrime International
CCIS
Common Channel Interoffice Signaling
CCITT
See Consultative Committee for International Telephone and Telegraph.
CCITT V.1
Defines binary 0/1 bits as space/mark line conditions
CCITT V.10
Unbalanced high-speed electrical interface characteristics (RS-423)
CCITT V.100
Interconnection between PDNs and PSTNs (Public Data Networks, Public Switched Telephone Networks)
CCITT V.11
Balanced high-speed electrical characteristics (RS-422)
CCITT V.110
ISDN terminal adaption
CCITT V.120
ISDN terminal adaption with statistical multiplexing
CCITT V.13
Simulated carrier control (full duplex modem used as half duplex) V.32 and V.33 compliant modems that support V.13 can be used in sync IBM RJE environments, so these networks, too, can take advantage of V.32/V.33 technology.
CCITT V.14
Asynchronous to synchronous conversion
CCITT V.15
Acoustic couplers
CCITT V.16
Electrocardiogram transmission on phone lines
CCITT V.17
Application-specific modulation scheme for Group 3 fax (Provides 2-wire half-duplex trellis-coded transmission at 7200, 9600, 12000, and 14400 bps.)
CCITT V.19
DTMF modems (low-speed parallel transmission)
CCITT V.2
Limits power levels of modems used on phone lines
CCITT V.20
Parallel data transmission modems
CCITT V.21
300 bps modems
CCITT V.22
1200/600 bps FDX modems Synchronous/asynchronous data transmission, full-duplex operation over 2-wire leased or dialup lines; 1200-bps data rate. Small businesses can beat the expense of leased lines by using V.22 modems with dialup lines. If they later add a 2-wire leased line, they can still use this modem. V.22 accomidates the equipment found in today's typical "hybrid" network: synchronous mainframes and terminals, and asynchronous PCs.
CCITT V.22BIS
Similar to CCITT V.22, but doubles the data throughput - 2400 bps modems. See CCITT V.22.
CCITT V.23
1200/75 bps (host tx 1200, rx 75, terminal tx 75, rx 1200). Also supports 600bps in the high channel speed. V.23 is used in Europe to support some videotext applications. Intel modems do not support the V.23 standard.
CCITT V.230
General data communications interface, layer 1
CCITT V.24
Known as EIA RS-232 in the USA. V.24 defines only the functions of the circuits. EIA-232-E (which is how the current version of the standard is designated) also defines electrical characteristics and connectors. The 232-equivalent electrical characteristics and connectors are defined in ISO 2110.
CCITT V.25
Automatic answering equipment and parallel automatic dialing (defines the 2100Hz "answer tone" that modems send) Enable any computer, sync or async, to perform autodialing functions with a V.25 compliant modem. See CCITT V.25bis.
CCITT V.25BIS
Serial automatic calling and answering-CCITT equivalent of AT commands (This is the current CCITT standard for modem control by computers via serial interface. The Hayes AT command set is used primarily in the USA.) Enable any computer, sync or async, to perform autodialing functions with a V.25 compliant modem. See CCITT V.25.
CCITT V.26
2400 bps 4W modems
CCITT V.26BIS
2400/1200 bps HDX modems
CCITT V.26TER
2400/1200 bps FDX modems
CCITT V.27
4800 bps 4W modems
CCITT V.27BIS
4800/2400 bps 4W modems
CCITT V.27TER
4800/2400 bps FDX modems (Also used in half-duplex 2-wire mode to implement the 2400 and 4800 bps transmission schemes in Group 3 fax.)
CCITT V.28
Electrical characteristics for V.24
CCITT V.29
9600 bps 4W modems (Also used in half-duplex 2-wire mode to implement the 7200 and 9600 bps transmission schemes in Group 3 fax.)
CCITT V.31
Older electrical characteristics (rarely used)
CCITT V.31BIS
V.31 using optocouplers
CCITT V.32
9600/4800 bps FDX modems Synchronous/asynchronous data transmission, full-duplex operation over 2-wire leased or dialup lines; 9600-bps data rate (fallback to 4800). The first universal standard for 9600-bps modems on dialup or leased phone lines. V.32 compliant modems are the industry standsrd for high-speed networks. Trellis encoding modulation allows high data speeds and reduces errors.
CCITT V.32BIS
4800, 7200, 9600, 12000, and 14400 bps modems and rapid rate renegotiation Synchronous/asynchronous data transmission, full-duplex operation over 2-wire leased or dialup lines; 14400-, 12000-, 9600-, 7200-, 4800-bps data rates. It offers two advantages over V.32. First, it transmitts data faster. Second, it redefines modem-connection negotiations (called training and retraining). Training is the procedure two modems use to make a connection; they "discuss" and "agree on a data rate. Retraining is a subsequent negotiation after data exchange is under way: both modems "agree" to reduce transmission to a lower speed to overcome ambient line noise. Retraining is triggered by line noise. After modems retrain, data transfer resumes. It also provides for a procedure called "fastrain", which allows the modem to fall either backward to a slower speed or forward to a faster speed. When two modems do a fastrain, they stop, determine that they can run faster, and then switch speed in a few milliseconds.
CCITT V.33
14400 bps (and 12000 bps for 4-wire leased lines) Uses the same signal modulation technioques that are used by V.32 modems, but are restricted to 4-wire leased lines.
CCITT V.34
Synchronous/asynchronous data transmission, full-duplex operation over 2-wire leased or dialup lines with automatic fallback to compatible lower modems such as V.32bis, V.32, and V.22bis. V.34 supports speeds from 2.4 Kbps to 28.8 Kbps. Modems using V.34 constantly assess the conditions on the line and implement various combinations of 10 new signal modulation techniques to compensate for line interference on-the-fly. They can transmit uncompressed data at speeds up to 28,800bps via ordinary dialup lines. Techniques used include Line Probing, Shell Mapping, and Train Recovery.
CCITT V.35
"Data Transmission at 48 Kbps Using 60- to 108-Khz Group-Band Circuits". It is typically used for DTEs or DCEs that interface to a high-speed digital carrier, such as AT&T Dataphone Digital Service (DDS) (The CCITT no longer recommends the use of this standard. It was made obsolete by V.36.)
CCITT V.36
48 kbps 4W modems
CCITT V.37
72 kbps 4W (V.36 and V.37 are not really "4w modems." They are group band modems, which means they combine several telephone channels.)
CCITT V.4
Sequence of bits within a character as transmitted
CCITT V.40
How teletypes indicate parity errors
CCITT V.41
An older, obsolete error control scheme
CCITT V.42
Error correcting procedures for modems using asynch-to-synch conversion (V.22, V.22bis, V.26ter, V.32, V.32bis); defines LAPM protocol and provides fallback to MNP4
CCITT V.42BIS
Lempel-Ziv-based data compression scheme for use with V.42 LAPM
CCITT V.5
Standard synchronous signaling rates - dialup lines
CCITT V.50
Standard limits for transmission quality for modems
CCITT V.51
Maintenance of international data circuits
CCITT V.52
Apparatus for measuring distortion and error rates for data transmission
CCITT V.53
Impairment limits for data circuits
CCITT V.54
Loop test devices for modems
CCITT V.55
Impulse noise measuring equipment
CCITT V.56
Comparative testing of modems
CCITT V.57
Comprehensive test set for high speed data transmission
CCITT V.6
Standard synchronous signaling rates - leased lines
CCITT V.7
List of modem terms (in English, Spanish, French)
CCR
See Commitment, Concurrency, and Recovery.
CCS
See Common Channel Signaling.
CCTV
Closed Circuit Television
CD
See Carrier Detect.
CD-I
See Compact Disc-Interactive.
CD-ROM
See Compact Disc-Read Only memory.
CD-ROM XA
See Compact Disc-Read Only Memory eXtended Architecture.
CDI
See Compact Disc-Interactive.
CDMA
See Code Division Multiple Access
CDPD
Cellular Digital Packet Data
CDR
CorelDRAW file suffix - .cdr.
CDTV
See Commodore Dynamic Total Vision.
CE
(Arpus/ce) X editor from Enabling Technologies Group. Runs on many UNIX platforms.
CECP
See Country Extended Code Page.
CEMM.EXE
A 386 expanded memory manager provided with all Compaq 386 computers.
CENTRAL OFFICE
(CO) The central office is a facility that serves local telephone subscribers. In the CO, subscribers' lines are joined to switching equipment that allows them to connect to each other for both local and long distance calls.
CENTRAL PROCESSING UNIT
(CPU) The processor that controls a computer. In an Intel-based computer, this is the 80x86 processor that runs the operating system and controls all internal devices. In a minicomputer or mainframe environment, this is the processor (or multiprocessor computer) where processing takes place for all users.
CENTRALIZED PROCESSING
In a minicomputer or mainframe environment, processing is conducted in one (or in a few) CPUs. User devices are 'terminals' that provide multiple-user access to one centralized processing.
CENTREX
Centrex is a type of business telephone service. It is like having a PBX located in your local central office. Centrex is basically single line telephone service delivered to individual desks (the same as you get at your house) with additional features.
CERT
See Computer Emergency Response Team.
CGA
See Color Graphics Adapter.
CGI
Common Gateway Interface
CGM
See Computer Graphics Metafile.
CHANNEL SERVICE UNIT
Digital DCE used to terminate digital circuits (such as DDS or T1 lines) at the customer site.
CHAOS
CHAOS Protocol
CHAP
Challenge Handshake Authentication Protocol
CHARACTER-BASED INTERFACE
The traditional user interface common to non-Windows applications, where all screen images are made up of text characters.
CHARGE-COUPLED DEVICE
(CCD) Semiconductor device capable of transporting finite isolated charge-packets from one position to adjacent position by sequential clocking of an array of gates; charge-packets considered minority carriers with respect to semiconductor substrate. A semiconductor device consisting of an array of photo-sensors which generate an electrical charge proportional to the amount of light striking them.
CHARGE-INJECTION DEVICE
(CID) Specific fabrication scheme for solid-state image sensors; photo-generated charge sensed by injecting it from sensor into substrate.
CHARGEN
Character Generator Protocol
CHECK DIGIT
A digit included within a symbol whose value is based mathematically on other characters included in the symbol. It is used to mathematically check theaccuracy of a symbol.
CHECKSUM
A small integer value computed from a sequence of octets by treating them as integers and computing the sum. A checksum is used to detect errors that result when the sequence of octets is transmitted from one machine to another. Typically, protocol software computes a checksum and appends it to a packet when transmitting. When received, the protocol software verifies the contents of the packet by recomputing the checksum and comparing the value sent. Many TCP/IP protocols use a 16-bit checksum computed with one's complement arithmetic with all integer fields in the packet stored in network byte order.
CHILD VLM
Child VLMs handle a particular implementation of a logical grouping of functionality. For example, each NetWare server type has its own child VLM:
* NDS.VLM, for NetWare Directory Services™-based (NetWare v4.0) servers.
* BIND.VLM, for bindery-based servers (including NetWare v3.12).
* PNW.VLM, for NetWare desktop-based servers.
Various implementations of transport protocols also have their individual child VLMs. For example, IPXNCP.VLM handles IPX services, and TCPNCP.VLM handles TCP functions.
CHMOD
Change modes of files (file protection)
CHORD
A straight line segment whose end points coincide with the end points of a given arc.
CHORD ANGLE
A gage operation which measures the angle, with respect to horizontal, of the chord whose end points are determined by the positions of two features located along a circular gage.
CHROMA, CHROMINANCE
The color portion of the video signal that includes hue and saturation information. Requires luminance, or light intensity, to make it visible.
CICS
Customer Information Communication System. See CICS/MVS.
CICS/MVS
See Customer Information Control System (for MVS). See Multiple Virtual System.
CID
See Charge-Injection Device.
CID
See Configuration, Installation and Distribution.
CIE
See Commission International de l'Eclairage.
CIR
See Committed Information Rate.
CIRCUIT COMMON
See zero signal reference
CIS
See Card Information Structure.
CISC
See Complex Instruction Set Computing.
CISCO-FNA
CISCO FNATIVE
CISCO-SYS
CISCO SYSMAINT
CISCO-TNA
CISCO TNATIVE
CLAMPING VOLTAGE
The predefined voltage level at which a clamping circuit will activate.
CLEAN STARTUP DISKETTE
A diskette known to be uninfected, that contains the coded instructions from which the computer can be started.
CLEAR TO SEND
See CTS
CLICKSTREAMS
The paths a user takes as he or shee navigates cyberspace. Advertisers and online media providers are developing software that can accurately track users' clickstreams.
CLIENT
(Internet) An application that performs a specific Internet function. Examples include: gopher, mail, ftp, and Whois.
CLIENT
(Network) A system component that requests services from one or more of any type of server on a network. A stand-alone workstation that uses the services of any type of server on a network.
CLIENT APPLICATION
The application that initiates a DDE conversation. Any Windows application that can accept, display, and store Object Linking and Embedding (OLE) objects.
CLIENT-SERVER MODEL
A common way to describenetwork services and the model user processes (programs) of those services. Examples include the name-server/name-resolver paradigm of the DNS and file- server/file-client relationships such as NFS and diskless hosts.
CLIENT/SERVER COMPUTING
A mode of distributed network computing in which an application is executed cooperatively by two computers. The client component of the application (the front end) executes on one node, while the server component (the back end) runs on a second node. For PCs, communications between the nodes is implemented most frequently using the named pipes interprocess communication (IPC) protocol. Client/server computing allows more effective use of computing resources, higher performance, greater flexibility, simpler upgrades, and (for some applications) greater reliability and data integrity.
CLNP
Connectionless Network Protocol. The OSI protocol for providing the OSI Connectionless Network Service (datagram service). CLNP is the OSI equivalent to Internet IP, and is sometimes called ISO IP.
CLNS
Connectionless-mode Network Services
CLOCK
DCNET Time Server Protocol
CLOCK SPEED
The rate in which the computer clock oscillates, usually given in MHz (one million cycles per second). The computer's clock rate is a prime determinant of overall processing speed. Typical clock speeds for AT-compatibles are 6, 8, 10, 12, 16, and 20 MHz; for 80386 machines, typical speeds are 16, 20, 25, and 33 MHz.
CLOSET
Telecommunication closet is the recognized cross-connect between the backbone and horizontal cabling.
CLTP
Connectionless Transport Protocol. Provides for end-to-end Transport data addressing (via Transport selector) and error control (via checksum), but cannot guarantee delivery or provide flow control. The OSI equivalent of UDP.
CLUSTER CONTROLLER
Also known as a control unit (IBM model numbers 3174, 3172, 3274). A machine that supervises terminals and other peripherals. When personal computers are connected to a host computer through a gateway, the gateway server functions as a cluster controller.
CLV
See Constant Linear Velocity.
CMC
Construction Maintenance Center
CMIP
See Common Management Information Protocol
CMIS
Common Management Information Service
CMOL
CMIP on IEEE 802.2 Logical Link Control
CMOS RAM
A RAM chip that uses the complementary metal-oxide semiconductor process, which provides high speed and extremely low power consumption, making the chip useful for hardware such as the microcomputer clock.
CMOT
Common Management Information Protocol Over TCP/IP. An effort to use the OSI network management protocol to manage TCP/IP networks.
CMP
Compare two files (UNIX command)
CMT
Connection Management.
CMYK
Cyan, Magenta, Yellow, and black. The four process colors that are used in four-color printed reproduction.
CNA
See Customer Name and Address.
CNID
Calling Number IDentification
CO
See Central Office.
CO LINES
Lines connecting your office to your local telephone company's Central Office which in turn connects you to the nationwide phone system.
COAXIAL CABLE
A cable consisting of a central conductor surrounded by an insulator and then by another grounded conductor. The outer cable acts as a shield to prevent interference from reaching the inner conductor. Often used in Ethernet and ARCnet installations, and as with twisted pair, coax is the product of its physical properties. Among these properties are impedance, attenuation, capacitance, time delay, and velocity of propagation. The attenuation in coax cable is a function of the cable's conductor and insulation. Foam-core Teflon has the lowest attenuation, although solid-core Teflon is almost as low. Using foam core rather than solid core coax cable typically results in a 25 percent increase in cable performance. Coax cable types are differentiated by impedance values. Impedance, measured in ohms, concerns the relationship of current and voltage in a coax cable. The impedance of the cable used must match the impedance expected by the network cards. Use of a cable with a different impedance will greatly shorten the maximum distances across which the network cards will be effective. For instance, most Ethernet installations use 50-ohm cable, while ARCnet installations use 93-ohm cable. Impedance matching should also be observed in selecting the barrel connectors used in splicing coax, although in most cases the length is usually small enough for impedance to be considered insignificant. The connectors installed on coax are either crimp-on or twist-on. Crimp-on connectors are more reliable but require the proper tools and experience to install. The easier-to-install twist-on connectors provide a viable solution but have a greater tendency to become loose. Capacitance is classified by the dimensions of the inner and outer conductors and the dielectric constant of the core. Within the operating limits of a particular topology, the lower the capacitance, the longer the cable can be. Coax cable is as susceptible as twisted pair to electrical interference from things such as fluorescent light ballasts and copier machines.
COBWEB SITE
A World Wide Web page that hasn't been updated for along time. A dead Web page.
COCOT
Customer Owned Coin Operated Telephone
CODE 128
A symbology representing the full128 ASCII character set. Numeric data may be represented in a double density mode where two digits are represented by one character.
CODE 39
Analphanumeric symbology recognized by most nations,widely used in the manufacturing industry.
CODE DIVISION MULTIPLE ACCESS
(CDMA) Wideband spread-spectrum technology, providing caller ID, voice mail and short messaging services. Multiple conversations are spread over a wide segment of the specturm so that many users simultaneously share a 1.25mhz-wide channel. Each signal is assigned a different spreading code to differentiate one call from another.
CODE PAGE
For MS-DOS version 3.3 and later, a table that relates the keys on the keyboard to the characters displayed on the screen, thereby providing support for the character sets and keyboard layouts used in different countries. Code page 437 is the code page for the United States.
CODEC
An assembly with an encoder and a decoder in the same equipment used for compression/decompression of video (in DVI).
COE
Central Office Equipment
COLD BOOT
Using the Reset button, it generally restarts the boot process, including the POST. However, this procedure does not necessarily discontinue power to the motherboard. If the power is not interrupted, the cold boot may fail to reset all adapters in the computer's adapter slots. To ensure that all adapters are properly reset, you should use the power switch to turn the computer off. Leaving the power off for ten seconds ensures that all the capacitors on the motherboard have time to discharge and should also give the hard disk drive a chance to stop spinning. Using reboot methods such as CTRL+ALT+DEL (See Warm Boot) or the Reset button is acceptable when a hardware problem is not suspected.
COLLECTION OBJECT
A set of objects that can be referred to as a unit.
COLLIMATE
To make rays of light parallel.
COLLISION
An event that occurs when two computers attached to a network attempt to send information or access a resource simultaneously.
COLLISION DETECT
A signal indicating that one or more stations are contending with the local station's transmission. The signal is sent by the physical layer to the data link layer on an Ethernet/IEEE 802.3 node.
COLOR BALANCE
The process of matching the amplitudes of red, green and blue signals so the resulting mixture makes an accurate white color.
COLOR CYCLING
A means of simulating motion in a video by changing colors.
COLOR GRAPHICS ADAPTER
A low-resolution video display standard, invented for the first IBM PC. CGA pixel resolution is 320x200.
COLOR KEYING
To superimpose one image over another for special effects.
COM PORTS
See Communication Ports.
COMMAND INTERFACE
A user interface that requires the user to enter commands at the command prompt. Also called command-line interface.
COMMAND MODE
One of the two operating modes of the modem, sometimes called local mode or terminal mode. (The other is on-line mode.) In command mode, the modem interprets any information it receives from the local computer (or terminal) as modem commands. It tries to perform the commands sent to it, and it returns result codes indicating the results of the commands. The modem enters command mode when you turn on or reboot your computer (or terminal), or when you type the escape sequence (normally +++) while the modem is in on-line mode.
COMMAND PROMPT
A screen symbol such as C:> that requests user input. Also called the MS-DOS prompt.
COMMAND-REPLY PAIR
The combination of messages normally occurring on a communication network; the first message asks for work to be done, the second message (from the station receiving the command message) gives information on the status of the work. If completed successfully, it will be accompanied by any data requested; if completed unsuccessfully, it will indicate the reason for the failure.
COMMISSION INTERNATIONAL DE L'ECLAIRAGE
The international commission on illumination. Developer of color matching systems.
COMMITMENT, CONCURRENCY, AND RECOVERY
(CCR) An OSI application service element used to create atomic operations across distributed systems. Used primarily to implement two-phase commit for transactions and nonstop operations.
COMMITTED INFORMATION RATE
In frame relay, when the router slows data traffic at a user defined, pre-determined rate due to congestion.
COMMODORE DYNAMIC TOTAL VISION
Consumer multimedia system from Commodore that includes CD-ROM/CD audio player, Motorola 68000 processor, 1MB RAM, and 10-key infrared remote control.
COMMON CARRIER
A private utility that furnishes communications services to the general public.
COMMON CHANNEL SIGNALING
An integral part of ISDN known as "Signaling System 7", CCS is a method for sending call-related information between switching systems by means of a dedicated signaling channel. This signaling channel is separate from the bearer or B channels. CCS allows services such as call forwarding and call waiting to be provided anywhere in the network. Other acronyms for Common Channel Signaling are: CCSS, CCSS7 and SS7.
COMMON MANAGEMENT INFORMATION PROTOCOL
(CMIP) The OSI network management protocol.
COMMUNICATION PORTS
The connectors and accompanying circuitry on your computer that let you connect serial devices (usually serial printers, modems, or mice) to your computer and communicate with these devices. Communication ports are also called serial ports. To keep track of the devices, DOS assigns names that begin with the letters COM to communication ports (such as COM1 and COM2).
COMMUNICATION SERVER
A dedicated, standalone server that manages communications activities for other computers.
COMMUNICATIONS CONTROLLER
Also known as a front-end processor (IBM model numbers 3725, 3745, 3705, 3720). In remote environments, a machine directly attached to a host computer, that processes communication requests.
COMMUNICATIONS SOFTWARE
A program that sets up your modem and gives you a human interface to the various functions of your modem. Examples of DOS-based communications programs are Smartcom, Procomm, and Crosstalk. Examples of communications programs for the Macintosh are Quick Link II, MicroPhone, and Red Ryder.
COMPACT DISC-INTERACTIVE
(CDI) A compact disc format (developed by NV Philips and Sony Corporation) which provides audio, digital data, still graphics and limited motion video.
COMPACT DISC-READ ONLY MEMORY
(CD-ROM) A standard medium for storing digital data in machine readable form, accessible with a laser-based reader. A 4.75 inch laser-encoded optical memory storage medium. Uses CLV format and can hold about 550 megabytes of data.
COMPACT DISC-READ ONLY MEMORY EXTENDED ARCHITECTURE
An extension of the CD-ROM standard, billed as a hybrid of CD-ROM and CD-I and promoted by Sony and Microsoft. The extension adds ADPCM audio to permit the interleaving of sound and video data. It is an essential component of Microsoft's plan for multimedia computers.
COMPANION FILE VIRUS
The virus known as AIDS II takes advantage of a feature of DOS where if a program exists in both .COM and .EXE files in the same directory, the .COM program is executed. A companion file virus does not actually infect program files. Instead, when a user types the name of a program (expecting to execute a program in an .EXE file), the virus in a .COM file of the same name executes, finds another .EXE file, and makes a copy of itself in a companion .COM file for that .EXE file. The virus sets the hidden attribute of the companion file prevent users from seeing the file in a DIR listing.
COMPLEX INSTRUCTION SET COMPUTING
(CISC) Microprocessor architecture that the Intel 80X86 chips use. Contrast with RISC.
COMPOSITE VIDEO
A video signal format that includes the complete visual waveform, including : chrominance (color), luminance (brightness), blanking pedestal, field, line, color sync pulses and field qualizing pulses.
COMPOUND DOCUMENT
A document that contains multiple sources of information (embedded and linked data) that was created in other kinds of applications.
COMPOUND DOCUMENT
A file that has more than one element (text, graphics, voice, video) mixed together.
COMPRESSED VIDEO
A digital video image or segment that has been processed using a variety of computer compression algorithms and other techniques to reduce the amount of data required to accurately represent the video content.
COMPRESSION
The translation of data (video, audio, digital, or a combination) to a more compact form for storage or transmission.
COMPUTER + SCIENCE NETWORK
(CSNET) A large computer network, mostly in the U.S. but with international connections. CSNET sites include universities, research labs, and some commercial companies. Now merged with BITNET to form CREN. See BITNET.
COMPUTER EMERGENCY RESPONSE TEAM
Formed by the Defense Advanced Research Projects Agency (DARPA) in November 1988 in esponse to the needs exhibited during the Internet worm incident.
COMPUTER GRAPHICS METAFILE
A standard format that allows for the interchanging of graphics images.
COMPUTER SUPPORT COLLABORATION
Describes computers that enhance productivity for people working in groups. Application examples include video conferencing, video mail, and shared workspaces.
CONCENTRATOR
Computers on a twisted pair system are connected to each other using a hub, known as a concentrator.
CONFIGURATION PROFILE
The current operating characteristics of your modem, stored in the modem's S-registers. Whenever you issue a modem command to change one of the operational characteristics (such as setting the volume control or turning the speaker on or off), the modem changes the values in the S-registers to reflect your changes.
CONFIGURATION TIMER
A configurable timer in the OSI protocol that invokes the sending of an ESH (End System Hello) or an ISH (Intermediate System Hello).
CONFIGURATION, INSTALLATION AND DISTRIBUTION
(CID) An IBM architecture for standard LAN installation and configuration operations. The portions of CID implemented by the LAN Distance product are (1) installation from a redirected drive and (2) use of a response file.
CONNECTED SOCKET
A socket which has been bound to a permanent destination. See also Socket.
CONNECTION
A communication session established between a server and a workstation. An NCP request issued by the DOS workstation shell or OS/2 Requester is answered by the NCP layer of the server, and the server allocates a connection for the workstation. Messages are then passed through the connection, much in the same way a mailbox is used. Once the connection is established, NCP packets communicate between workstations and servers, without regard to the layers of protocol or physical media that lie between the two. This is a session-layer function equivalent to layer 5 of the OSI model. (See OSI Model, UNA, and NCP.)
CONNECTION MANAGEMENT
(CMT) A protocol function of the FDDI interface card that establishes the physical connections between the stations.
CONNECTION ORIENTED SYSTEM
A network in which two nodes establish a session before they communicate. During the session, the two nodes communicate only with each other. When the transmission is complete, the session is ended.
CONNECTION-ORIENTED
The model of interconnection in which communication proceeds through three well-defined phases: connection establishment, data transfer, connection release. Examples: X.25, Internet TCP and OSI TP4, ordinary telephone calls.
CONNECTION-ORIENTED PROTOCOL
A networking protocol that communicates in two directions, each packet being sent requiring an acknowledgment packet. (See connectionless protocol, NCP, and SPX.)
CONNECTIONLESS
A form of interconnection that allows communication to take place without first establishing a connection. The model of interconnection in which communication takes place without first establishing a connection. Sometimes (imprecisely) called datagram. Examples: LANs, Internet IP and OSI CLNP, UDP, ordinary postcards.
CONNECTIONLESS PROTOCOL
A networking protocol that communicates in one direction only, not requiring an acknowledgment. (See IPX, connection-oriented protocol, NCP, and SPX.)
CONNECTIONLESS SYSTEM
A network type that treats each packet as an individual system communication (IPX, for example). Each packet contains a destination address, allowing it to be delivered independent of any other packet.
CONS
Connection-mode Network Services
CONSOLE
The device used to configure network devices at boot (start-up) time.
CONSTANT LINEAR VELOCITY
(CLV) Spiral format of audio compact disks and some video laser disks.
CONSULTATIVE COMMITTEE FOR INTERNATIONAL TELEPHONE AND TELEGRAPH
An international standards organization dedicated to creating communications protocols that will enable global compatibility for the transmission of voice, data, and video across all computing and telecommunications equipment
CONTAINER
Anything that contains other objects, either linked or embedded.
CONTEXT SWITCHING
The kind of multitasking that is done in standard mode Windows, where the CPU switches from one task to another, rather than allo cating time to each task in turn, as in timeslicing.
CONTINUOUS TONE
An image that has all the values (0 to 100%) of gray (black and white) or color in it. A photograph is a continuous tone image.
CONTRAST
The range between the lightest tones and the darkest tones in an image.
CONTROL ACCESS UNIT
See Star wired Ring.
CONTROL UNIT
See Cluster Controller.
CONTROL-UNIT TERMINAL
An IBM 3270 terminal attached to a cluster controller that processes its keystrokes and managers its buffers. A control-unit terminal can support one host communications session at a tine.
CONTROLLED-COLLAPSE CHIP CONNECTION
(C4) Often called Flip Chip, this technology attaches a chip with the circuitry side facing the substrate by reflowing solder bumps.
CONVENTIONAL MEMORY
The physical memory in a PC from 0K to 640K. See Base Memory.
CONVERGENCE
In an RGB monitor, where red, green, and blue signals all "converge" in one pixel. At full brightness, the RGB pixel in convergence would be white.
COOKIE-JAR
Authentication Scheme
COPYRIGHTED
The opposite of public domain. A copyrighted program is one where the author has asserted his or her legal right to control the program's use and distribution by placing the legally required copyright notices in the program and documentation. The law gives copyright owners broad rights to restrict how their work is distributed, and provides for penalties for those who violate these restrictions. Maintaining a copyright does not necessarily imply charging a fee, so it is perfectly possible and legal to have copyrighted programs which are distributed free of charge.
CORE GATEWAY
Historically, one of a set of gateways (routers) operated by the Internet Network Operations Center at BBN. The core gateway system forms a central part of Internet routing in that all groups must advertise paths to their networks from a core gateway, using the Exterior Gateway Protocol (EGP). See EGP, backbone.
CORPORATION FOR OPEN SYSTEMS
(COS) A vendor and user group for conformance testing, certification, and promotion of OSI products.
CORRUPTED FILE
A file that has been damaged.
COS
See Corporation for Open Systems
COSINE
Cooperation for Open Systems Interconnection Networking in Europe. A program sponsored by the European Commission, aimed at using OSI to tie together European research networks.
COSMOS
Computer System for Main Frame Operations
COUNTRY EXTENDED CODE PAGE
(CECP) An 8-bit code page that has a standard 93-character set, extended to the multilingual character set for the national languages of some European countries.
COVERAGE
A feature (of the AT&T Merlin Legend system) that co-workers use to answer your calls from their phones and vice versa. See Individual Coverage and Group Coverage.
CPE
See Customer Premise Equipment.
CPU
An abbreviation for the computer's central processing unit.
CRAB
A program that attacks the data display on the computer terminal. A well-known example is a crab program for DOS machines that causes letters to drop to the bottom of the screen.
CRASH
To stop working irrevocably. The usual remedy is to switch off the power, switch it back on and start again. Also, what some programmers do after having spent 39 straight hours drinking Coke and playing Marble Madness.
CRC
Cyclic Redundancy Check
CREEPER
A worm-like program that is designed to spread across computer monitors and display "funny" messages on computer screens. An example of a creeper program that was popular on the ARPANET in the 1970s displayed the message I'm the creeper, catch me if you can! It was designed to spread from terminal to terminal until it was eradicated by a program called the reaper.
CREN
The Corporation for Research and Educational Networking. See BITNET and CSNET.
CREST FACTOR
Ratio of the peak amplitude to the RMS value or effective value of any periodic quantity such as a sinusoidal alternating current. Also known as amplitude factor and peak factor
CROSS REFERENCE
A type of hypertext link in Microsoft Help. A cross reference is a topic that appears in the Help window when you click on a term that appears in Help as green solid underlined text.
CROSS-CONNECT FIELD
A color-coded strip identifying the type of service carried on the cables terminated on a wire cross-connect terminal block. The color code is:
Green = central office trunks
Blue = station cables
Purple = ISN equipment, multiplesing devices, PBX ports
White = house cables
Yellow = auxiliary equipment (such as Application Processor)
Orange = multiplexor ports (Premises Lightwave System only)
Grey = tie cables (between riser/apparatus and satellite closets)
CROSSED PINNING
Cable configuration that allows two DTE devices or two DCE devices to communicate.
CROSSTALK
Noise passed between communications cables or device elements. Crosstalk occurs when the signal is reduced due to interference from other cable. It is rated using a decibel (db) loss index and is always active in twisted pair-especially in telephone wire. Crosstalk is measured by the amount of signal induced by an active or excited pair onto a quiet pair and can affect the suitability of twisted pair for computer use. The lower the db loss index, the stronger the signal becomes. In addition, the smaller the capacitance differences between pairs of cables, the lower the crosstalk effect becomes.
CRS
Configuration Report Server
CRSAB
Centralized Repair Service Answering Bureau
CRYPTOLOGY
The science of encryption and decryption.
CSC
See Computer Support Collaboration.
CSH
A shell (command interpreter) with C-like syntax
CSI
Computer Security Institute in San Frans
CSMA
See Carrier Sense/Multiple Access
CSMA/CA
See Carrier Sense/Multiple Access/Collision Avoidance
CSMA/CD
See Carrier Sense Multiple Access with Collision Detection
CSMA/CE
See Carrier Sense/Multiple Access/Collision Elimination
CSNET
See Computer+Science Network
CSNET-NS
CSNET Mailbox Nameserver Protocol
CSTA
Computer-Supported Telecommunications Applications.
CSU
See Channel Service Unit
CT
See Configuration Timer.
CTDMA
Concurrent Time Domain Multiple Access
CTERM
Command Terminal Protocol
CTI
Computer Telephony Integration.
CTIA
Cellular Telecommunication Industry Association
CTS
Clear to Send signal in RS-232-C. An RS-232C signal that tells the computer it can start sending information. A signal from a modem to a device that indicates the carrier is stable and the modem is ready to transmit. The device will not transmit until CTS is on. If CTS is turned off during transmission, the module will stop transmitting until CTS is restored.
CTS
See Clear To Send.
CURRENT LOOOP
Method of interconnecting terminals and transmitting signals: a mark (binary 1) is represented by current on the line, and a space (binary 0) is represented by the absence of current.
CURRENT SINK
A signal sending device that shunts current to ground.
CURRENT SOURCE
A signal sending device that generates positive current.
CUSTOMER INFORMATION CONTROL SYSTEM (FOR MVS)
(CICS/MVS) An IBM host-based transaction processing environment. The MCS system executes in this environment. See Multiple Virtual System.
CUSTOMER NAME AND ADDRESS
(CNA) The CNA number is a phone number for telephone company personnel to call and get the name and address for a phone number. If a telephone lineman finds a phone line he does not recognize, he can use the ANI number to find it's phone number and then call the CNA operator to see who owns it and where they live.
CUSTOMER PREMISE EQUIPMENT
Telephone equipment (key systems, PBXs, NT-1s, answering machines, etc.) which reside on the customer's premises. "Premises" might be anything from an office to a factory to a home.
CUSTOMER PROVIDED EQUIPMENT
See Customer Premise Equipment.
CUT
See Control-Unit Terminal.
CUT-AND-PASTE
A method of moving data into another document or file, which could be for a different but compatible application.
CUT-THROUGH
Technique for examining incoming packets whereby an Ethernet switch looks only at the first few bytes of a packet before forwarding or filtering it. This process is faster that looking at the whole packet, but allows some bad packets to be forwarded.
CYCLE-TIME
Refers to the time it takes to move 32-bits from the hard drive buffer to main memory. Each sector contains 512 bytes. To transfer a sector requires 128 cycles.